• Structural Engineering and Mechanics
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• 제20권5호
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• pp.575-587
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• 2005

Using the nonlinear load transfer function for pile side soil and the linear load transfer function for pile end soil, a combined approach of the incremental load transfer matrix method and the approximate differential equation solution method is presented for the nonlinear analysis of interaction between flexible pile group and soil. The proposed method provides an effective approach for the solution of the nonlinear interaction between flexible pile group under rigid platform and surrounding soil. To verify the accuracy of the proposed method, a static load test for a nine-pile group under a rigid platform is carried out. The finite element analysis is also conducted for comparison purposes. It is found that the results from the proposed method match very well with those from the experimental test and are better in comparison with the finite element method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.164.2-164
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• 2001

Sliding mode control (SMC) with variable nonlinear boundary layer is proposed. Two Fuzzy logic controllers (FLCs) are used to decide both boundary layer thickness and nonlinear interpolation using sigmoid function in the boundary layer. The nonlinear interpolation in the boundary layer suing FLC reduces stead state error and chattering. Sigmoid function is used to nonlinear interpolation in the boundary layer sigmoid function parameter with FLC. To demonstrate its performance, the Proposed control algorithm is applied to a simple nonlinear system.

• 응용통계연구
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• 제15권2호
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• pp.311-321
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• 2002

시계열 자료의 전이함수분석에 있어서 조건부 이분산성을 도입하고 기존의 선형 이분산모형인 Engle(1982)의 ARCH 모형과 더불어 비선형 모형인 베타-ARCH 및 분계점-ARCH모형을 고려하였다. 모형적합절차를 간략히 소개하였으며 제안된 모형을 미국 나스닥지수와 국내 종합주가지수에 적용시켜본 결과 비선형 ARCH 모형이 우수함을 알 수 있었다.

• Journal of information and communication convergence engineering
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• 제20권2호
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• pp.103-112
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• 2022

The goal of pattern mining is to identify novel patterns in a database. High utility itemset mining (HUIM) is a research direction for pattern mining. This is different from frequent itemset mining (FIM), which additionally considers the quantity and profit of the commodity. Several algorithms have been used to mine high utility itemsets (HUIs). The original BPSO algorithm lacks local search capabilities in the subsequent stage, resulting in insufficient HUIs to be mined. Compared to the transfer function used in the original PSO algorithm, the V-shaped transfer function more sufficiently reflects the probability between the velocity and position change of the particles. Considering the influence of the acceleration factor on the particle motion mode and trajectory, a nonlinear acceleration strategy was used to enhance the search ability of the particles. Experiments show that the number of mined HUIs is 73% higher than that of the original BPSO algorithm, which indicates better performance of the proposed algorithm.

• 대한전자공학회논문지
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• 제19권6호
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• pp.67-79
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• 1982

가우스 잡음의 출현시 PWM 시스템의 안정도가 연구되었다. 일반 시스템은 종래의 서술 함수 방법을 이용할 때 비선형 소자와 선형 소자로 나누어진다. 등가 어드미턴스 개념이 이 시스템의 비선형 소자의 전달 특성을 구하는데 사용되었다. 이 논문에서는 가우스 잡음만이 존재하는 경우 자기 발진 조건이 유도되었고 그 결과를 컴퓨터 시뮬레이션으로 분석하였다. The stability of general pulse-width modulation system with Gaussian random disturbance was discussed . General system is divided into nonlinear and linear elements using the conventional describing function method. The concept of the equivalent admittance was used to find the transfer characteristic of the nonlinear element of the system. In this paper the self-sustained oscillation condition in the autonomous system was derived and the results was analyzed with computer simulation.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1280-1286
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• 2004

A lot of industrial chemical processes contain certain input nonlinearities even though they are controlled by several linear controllers. Here we investigate a sequential loop closing identification method for MIMO Hammerstein nonlinear processes with diagonal nonlinearities. The proposed method separates the identification of the nonlinear static function from that of the linear subsystem by using a relay feedback test and a triangular type signal test. From 2 n activations for n n MIMO nonlinear processes, we sequentially identify the whole range of the nonlinear static function as well as the transfer function matrix of the linear subsystem.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1172-1177
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• 1993

Dynamic characteristics of a hydraulic power supply are studied theoretically and computationally. The transfer function between the supply pressure and the load flow is derived considering relief valve dynamics, accumulator dynamics, and flow line dynamics. Frequency responses and time responses are obtained in many conditions using the transfer function and nonlinear mathematical model respectively.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.393-396
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• 2004

This paper proposed a transfer function of a frequency-controlled resonant inverter for output power control. The inverter is modeled as an equivalent circuit by using Phasor transformation. A transfer function is derived from the equivalent circuit which contains cross-coupled nonlinear parts. By simulation of the circuit, the transfer function can be approximated as a linear first-order function. The proposed transfer function is verified through comparison of experimental and simulation results.

• 한국추진공학회지
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• 제15권6호
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• pp.98-106
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• 2011

본 논문에서는 많은 가스터빈 산업체 및 연구기관에서 연소불안정 현상과 관련된 변수들을 예측하기 위해 가장 보편적으로 이루어지고 있는 열음향 해석 모델에 대한 기술 소개 및 최근의 연구 동향을 분석하였다. 선형 시스템 해석을 통하여 연소 불안정이 발생하는 고유 주파수 및 불안정 초기 성장률의 예측이 가능하다. 이를 위하여 정의된 시스템에서의 음향파와 열발생율 섭동간의 선형 관계식을 선형 음향 이론으로부터 유도할 수 있고, 이 관계식의 해를 구하기 위해서 가장 중요한 부분은 화염 전달 함수로부터 n-${\tau}$ 함수를 구하여 열발생율 섭동 결과에 대한 정보를 얻는 것이다. 현재까지의 연구 결과로부터 선형 특성 해석에는 상당한 진보가 이루어져 왔고, 실제 가스터빈 연소기에 적용하는 노력이 있었으나, 한계 진폭과 과도기 현상 예측을 위해서 요구되는 비선형 동적 특성 모델링 기술 개발은 현재 간단한 연소기와 버너의 적용에 머물러 있는 실정이다. 실제 복잡한 가스터빈과 같은 연소 시스템에 적용되기 위해서는 비선형 경계 조건을 고려한 시스템 동적 특성 연구와 화염의 비선형 거동을 더욱 정확히 설명할 수 있는 전달 함수에 대한 예측 기술이 선행되어야 한다.

• Geomechanics and Engineering
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• 제7권2호
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• pp.149-164
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• 2014

One of the most advanced classes of techniques for ground response analysis is based on the use of Transfer Functions. They represent the ratio of Fourier spectrum of amplitude motion at the free surface to the corresponding spectrum of the bedrock motion and they are applied in frequency domain usually by FFT method. However, Fourier spectrum only shows the dominant frequency in each time step and is unable to represent all frequency contents in every time step and this drawback leads to inaccurate results. In this research, this process is optimized by decomposing the input motion into different frequency sub-bands using Wavelet Multi-level Decomposition. Each component is then processed with transfer Function relating to the corresponding component frequency. Taking inverse FFT from all components, the ground motion can be recovered by summing up the results. The nonlinear behavior is approximated using an iterative procedure with nonlinear soil properties. The results of this procedure show better accuracy with respect to field observations than does the Conventional method. The proposed method can also be applied to other engineering disciplines with similar procedure.